Methods and apparatuses for encoding and decoding audio signal

Abstract

Provided are methods and apparatuses for more efficiently encoding and decoding a high frequency band signal which is from an audio signal and which is greater than a predetermined threshold frequency. The method and apparatus for encoding the audio signal encodes a linear prediction coding (LPC) coefficient and gain information of a residual signal, which are generated by performing LPC analysis, thereby encoding a high frequency signal so as to have enhanced sound quality, while using less bits.

1 . A method of encoding an audio signal, the method comprising:
 performing linear predictive coding (LPC) analysis on a high frequency signal and outputting an LPC coefficient of the high frequency signal and a residual signal of the high frequency signal, the high frequency signal having a high frequency greater than a predetermined threshold frequency and being in the audio signal;   extracting gain information which indicates an amplitude variation of the residual signal; and   multiplexing the LPC coefficient, and the gain information.   
   
   
       2 . The method of  claim 1 , wherein the gain information is parameter information which is generated by modeling a time envelope of the residual signal. 
   
   
       3 . The method of  claim 1 , wherein the extracting of the gain information comprises:
 dividing a time envelope of the residual signal into units of predetermined time; and   generating a parameter that indicates the amplitude variation of the time envelope of the residual signal, by using an energy of each period of the units of predetermined time.   
   
   
       4 . The method of  claim 1 , further comprising encoding a low frequency signal of the audio signal, excluding the high frequency signal, by using a predetermined core coder. 
   
   
       5 . An audio signal encoding apparatus comprising:
 a linear predictive coding (LPC) analysis unit which performs LPC analysis on a high frequency signal and outputting an LPC coefficient of the high frequency signal and a residual signal of the high frequency signal, the high frequency signal having a high frequency greater than a predetermined threshold frequency and being in the audio signal;   a gain information extraction unit which extracts gain information which indicates an amplitude variation of the residual signal; and   a multiplexing unit which multiplexes the LPC coefficient, and the gain information.   
   
   
       6 . The audio signal encoding apparatus of  claim 5 , wherein the gain information extraction unit extracts parameter information, which is generated by modeling a time envelope of the residual signal, as the gain information. 
   
   
       7 . The audio signal encoding apparatus of  claim 5 , wherein the gain information extraction unit comprises:
 a division unit which divides a time envelope of the residual signal into units of predetermined time; and   an envelope parameter generation unit which generates a parameter that indicates the amplitude variation of the time envelope of the residual signal, by using an energy of each period of the units of predetermined time.   
   
   
       8 . The audio signal encoding apparatus of  claim 5 , further comprising a predetermined core coder which encodes a low frequency signal of the audio signal, excluding the high frequency signal. 
   
   
       9 . A method of decoding an audio signal, the method comprising:
 decoding a low frequency signal of the audio signal by using a predetermined core coder;   generating a residual signal of a high frequency signal of the audio signal by using the decoded low frequency signal;   decoding the high frequency signal by performing linear predictive coding (LPC) synthesis which uses an LPC coefficient of the high frequency signal in a bitstream and uses the residual signal; and   reconstructing the audio signal by integrating the decoded low frequency signal and the decoded high frequency signal.   
   
   
       10 . The method of  claim 9 , wherein the generating of the residual signal further comprises:
 performing spectral whitening with respect to the decoded low frequency signal, and generating a residual signal of the decoded low frequency signal;   copying the residual signal of the decoded low frequency signal to a predetermined high frequency band;   adjusting an envelope of a signal, which is copied to the high frequency band, by using gain information of the residual signal of the high frequency signal in the bitstream.   
   
   
       11 . The method of  claim 10 , wherein the gain information of the high frequency signal is parameter information which is generated by modeling a time envelope of the residual signal of the high frequency signal in the bitstream. 
   
   
       12 . The method of  claim 10 , wherein the adjusting of the envelope comprises:
 dividing the signal copied to the high frequency band into units of predetermined time; and   adjusting a time envelope of the signal copied to the high frequency band by adjusting an envelope of each period of the units of predetermined time of the signal copied to the high frequency band according to parameter information which indicates an energy of each period of a time envelope of the high frequency signal in the bitstream.   
   
   
       13 . The method of  claim 9 , wherein the decoding of the high frequency signal comprises performing the LPC synthesis by transforming the LPC coefficient in the bitstream into line spectral frequencies (LSFs) and then by interpolating the LSFs. 
   
   
       14 . An audio signal decoding apparatus comprising:
 a core decoder which decodes a low frequency signal of the audio signal;   a high frequency residual signal generation unit which generates a residual signal of a high frequency signal of the audio signal by using the decoded low frequency signal;   a linear predictive coding (LPC) synthesis unit which decodes the high frequency signal by performing LPC synthesis which uses an LPC coefficient of the high frequency signal in a bitstream and uses the residual signal; and   an integration unit which reconstructs the audio signal by integrating the decoded low frequency signal and the decoded high frequency signal.   
   
   
       15 . The audio signal decoding apparatus of  claim 14 , wherein the high frequency residual signal generation unit comprises:
 a spectral whitening performing unit which performs spectral whitening with respect to the decoded low frequency signal, and generates a residual signal of the decoded low frequency signal;   a high frequency band copy unit which copies the residual signal of the decoded low frequency signal to a predetermined high frequency band;   an envelope adjusting unit which adjusts an envelope of a signal, which is copied to the high frequency band, by using gain information of the residual signal of the high frequency signal in the bitstream.   
   
   
       16 . The audio signal decoding apparatus of  claim 15 , wherein the gain information of the high frequency signal is parameter information which is generated by modeling a time envelope of the residual signal of the high frequency signal in the bitstream. 
   
   
       17 . The audio signal decoding apparatus of  claim 15 , wherein the envelope adjusting unit divides the signal copied to the high frequency band in units of predetermined time, and adjusts a time envelope of the signal copied to the high frequency band by adjusting an envelope of each period of the units of predetermined time of the signal copied to the high frequency band according to parameter information which indicates an energy of each period of a time envelope of the high frequency signal in the bitstream. 
   
   
       18 . The audio signal decoding apparatus of  claim 14 , wherein the LPC synthesis unit performs the LPC synthesis by transforming the LPC coefficient in the bitstream into LSFs and then by interpolating the LSFs.